Can anyone give me some sort of grammatical reference to this usage of an ablative absolute where the noun or pronoun must be supplied from context? It seems very irregular to me; A&G cite specific instances in which this can occur, none of which seem applicable here.

vir litterarum wrote:...but it seems to me that equating it to an abl. of manner here is a stretch...

Is Ablative of Manner the same as Ablative Absolute? Also, I hear "[eo] defuncto" but "eo" is unnecessary from the context, for "with him dead but not buried [i.e., while he was...] ". (Merely proposing what I think, of course, which might be wrong.)Absolutum Ablativum, similene Actionis Ablativo est? Etiam, "eo defuncto" lego, quià de contextu pronomen intellegas. (Quod puto propono; falsum sit, certé fateor.)

You're right that it seems that "eo" must be understood from context, but I have not seen this occur before where the nominal element of an ablative absolute must be understood from context, nor have I seen instances cited in Latin grammars, except those such as you referenced in A&G which seem qualitatively different to me.

Wouldn't it perhaps be easiest to construe "defuncto" as a substantive adjective being used as a noun, to mean "the one having died"? (A&G 288) It seems to me an adjective used substantively in an Ablative Absolute is quite common -- "paucis interfectis" from Caesar springs readily to mind: "a few [i.e., men/soldiers] having been killed."

Mihi dolet -- sorry if my note was unclear. Yes, it is definitely an Ablative Absolute. But (correct me if I am wrong) you were asking if a noun/pronoun should be supplied from context, and I am suggesting that "defuncto," though a participial adjective, is functioning as the noun here so there is no need to go further.

right, so you're translating it, "also with dead body not even buried"? however, you're taking "necdum" as an adverb, whereas this commentary and the Loeb take it as equaling "et nondum," i.e. "even with [Drusus] dead and not yet buried."

No, as defuncto is the perfect passive participle from defungor, a deponent verb, and sepulto a perfect passive participle from sepelio, I would translate the phrase literally as:

"with the one [i.e., the man we've been talking about here = Drusus"] having died and not yet having been buried."

However, that would be the literal translation -- your less literal translation "even with [Drusus] dead and not yet buried" above is fine. There is always a trade-off between the literal translation, which clarifies the Latin, and a less literal/more elegant translation which sounds better to our ears and perhaps clarifies the meaning a bit better.

I am suggesting that "defuncto," though a participial adjective, is functioning as the noun here so there is no need to go further.

If it were functioning as a substantive, it would need to be translated with "with the dead body not even buried," not "with the one having died and not yet having been buried"; you're translating it as a participle modifying an understood pronoun "one" even though you're saying it is functioning as a noun. "Defuncto" either must mean "a dead body," or "having been buried," but in the latter translation it is functioning as a participle, not a noun.